Ceramics have great potential in industrial applications because they are superior in their hardness, chemical stability and refractory characteristics. Currently, most ceramics used in the industry are single phase ceramics. However, when using these single phase ceramics, they have the following drawbacks:
1. It is difficult to produce dense single phase ceramics with a small grain size. The strength of ceramics is proportional inversely to the square root of the grain size. That is, the strength becomes greater as the grain becomes smaller. The strength of ceramics, on the other hand, will decrease drastically as the amount of porosity increases. Therefore, the ceramics must be completely densified. During the densification process, however, the grainls often grow rapidly and the strength is affected as a result. PA1 2. The high temperature stability is not satisfactory. When the single phase ceramics are used at high temperatures, their grains will grow rapidly. Therefore, the strength of ceramics will be decreased the longer they are in use. PA1 3. Other than some partially stabilized zirconium oxides, the toughness of single phase ceramics usually is not high. Low toughness causes the ceramics to become brittle. This situation results in increased difficulties when using these single phase ceramics. PA1 1-99 weight % of a spinel phase; and PA1 99-1 weight % of an oxide phase, PA1 (a) mixing one or more oxide powders from each type of A.sub.2 O.sub.3 and BO oxide powder to give a mixed powder; PA1 (b) slip casting, die pressing, or cold-isostatic pressing the mixed powder to form a green body; and PA1 (c) calcining the green body at a temperature from 1000.degree. C. to 2000.degree. C. to form a ceramic composite containing a BA.sub.2 O.sub.4 spinel phase and an oxide phase; PA1 in which A and B are defined as above.
In order to overcome the above drawbacks, multi-phase ceramics, i.e. ceramic composites, have been developed. A ceramic composite consists of adding a ceramic additive into another ceramic base. The blended additive, correctly composed, can hinder the growth of grains and create a final product with a smaller grain size and better high temperature stability. Furthermore, because the additive has a different Young modulus than that of the ceramic base, the cracks will propagate in a twisted way. This will increase the toughness of the product. Currently, on the market, the ceramic composites include alumina/SiC whiskers and alumina/zirconia composites. The two phases in these systems do not react at high temperature or have only a limited reaction. These composites often have superior properties than the single phase ceramics. The drawback, however, is that they are more expensive.
Because of the single phase ceramics' drawbacks and the expense for the composites, the inventor, after long research, has invented an improved ceramic composite.
The main purpose of the invention is to provide a ceramic composite with excellent properties to be used in industry and to provide a preparation method to produce the ceramic composite. The advantages of this method include the use of cheap raw materials and simple, easily controlled production steps.